1. Field of the Invention
The present invention relates to a volute horn attached to a vehicle, such as an automobile, and to its method of manufacture.
2. Description of the Related Art
In a typical volute horn, a vibration generating unit vibrates a diaphragm member attached to a horn body causing a sound to be created. The sound is adjusted in a resonating unit and then transmitted to the outside as a horn sound. The resonating unit forms a volute path along which the sound travels.
Referring to FIG. 3, a conventional volute horn 5 is shown in which a cover 4 is interposed between a diaphragm 3 and the frame 6 of a resonating device so that the bottom of the sound path, which is open to the frame, is blocked. Horn body 1 includes a vibration generating unit 3a disposed within a housing 2. To assemble the conventional horn, the cover 4 is first attached to the horn body so that an air vibration chamber is formed. The frame 6 of the resonating device is then attached to the outer surface of the cover 4. With such a method of manufacture, it is difficult to form a high-quality resonating device, which does not impair the quality or loudness of the sound. Namely, it is difficult to bond the outer surface of the cover 4 to the bottom of the frame 6 of the resonating device in an airtight manner. The closer the bond is to being airtight, the better the quality of the sound. In addition, to determine whether these components are bonded in a sufficiently airtight manner, the volute horn is tested only after complete assembly. If the bonding is found to be defective, the entire volute horn including the horn body is rejected, thus decreasing yield and productivity, and therefore increasing cost.
In another manufacturing method, a base member is bonded and fixed in an airtight manner to the bottom of the frame of the resonating device, which bottom serves as the bottom of the sound path, so that the sound path is blocked. The thus-formed resonating device is then attached to the horn body. In such a volute horn, an air vibration chamber is formed between the horn body and the base itself, which blocks the sound path. Fine adjustment of sound quality, including the adjustment of a gap A, cannot be done before the air vibration chamber is formed, that is, before the resonating device is attached to the horn body. It must therefore be done after the resonating device has been attached. However, when the fine adjustment is made after the resonating device has been attached, the frame of the resonating device blocks the resonating device side of an armature at the center of the diaphragm. Therefore, a gap sensor cannot be disposed on the resonating device side. As a result, adjusting and testing of sound quality become extremely troublesome and complicated. Examples of volute horn devices include Japanese Utility Model Publication No. 5100 (1983), Japanese Patent Publication No. 46039 (1983), and Japanese Utility Model Publication No. 36458 (1976).